Valence and Ionic Lowest-Lying Electronic States of Isobutyl Formate Studied by High-Resolution Vacuum Ultraviolet Photoabsorption, Photoelectron Spectroscopy, and Ab Initio Calculations

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• 作者：M. A. 艢mia艂ek ; M. 艁abuda ; J. Guthmuller ; S. V. Hoffmann ; N. C. Jones ; M. A. MacDonald ; L. Zuin ; N. J. Mason ; P. Lim茫o-Vieira
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：August 13, 2015
• 年：2015
• 卷：119
• 期：32
• 页码：8647-8656
• 全文大小：400K
• ISSN：1520-5215

文摘

The highest resolution vacuum ultraviolet photoabsorption spectrum of isobutyl formate, C₅H₁₀O₂, yet reported is presented over the energy range 4.5鈥?0.7 eV (275.5鈥?18.0 nm) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series observed in the photoabsorption spectrum have been assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of isobutyl formate and are compared with a newly recorded photoelectron spectrum (from 9.0 to 27.0 eV). The value of the first ionization energy was determined to be 10.508 eV (adiabatic) and 10.837 eV (vertical). New vibrational structure is observed in the first photoelectron band, predominantly resulting from C鈥揙 and C鈺怬 stretches of the molecule. The photoabsorption cross sections have been used to calculate the photolysis lifetime of isobutyl formate in the upper stratosphere (20鈥?0 km), indicating that the hydroxyl radical processes will be the main loss process for isobutyl formate.